Relief device



Oct. 10, 1950 v, JQHNSQN 2,525,487

RELIEF DEVICE Filed Oct. 17, 1944 2 Sheets-Sheet l WITNESSES: INVENTCR ATTORNEY Oct. 10, 1950 H. v. JOHNSON 2,525,487

RELIEF DEVICE Filed Oct. 17, 1944 2 Sheets-Sheet 2 WITNESSES: INVENTOR @QW Henry Mfohnsan.

BY a ATTORNEY Patented Oct. 10, 1950 RELIEF DEVICE Henry V. Johnson, Sharon, Pa., assignor to Westinghouse Electric Corporation, a corporation of Pennsylvania Application October 17, 1944, Serial No. 559,091

8 Claims.

This invention relates to relief devices and particularly to such devices adapted for use on electrical apparatus such as transformers.

In electrical apparatus, such as transformers, it is customary practice to partially fill the apparatus casing with an insulating and cooling fluid, such as oil, in which the apparatus is immersed. It is also customary to provide a relief diaphragm placed at the upper part of the easing that is adapted to rupture and relieve excessive pressures from the tank or casing, such as may be caused by the disintegration of the insulating liquid due to electrical disturbances such as stewing arcs or other arc discharges caused by failure of the insulating material re sulting in the formation of gas. This use of a pressure release device prevents the casing from rupturing due to excessive internal pressures therein.

Such diaphragms have been made of thin sheets of Micarta and certain metals, such as copper, aluminum, etc., and also of glass. The pressure at which such diaphragms rupture is a function of the material of which the diaphragm is made and also of the area, thickness and shape of the diaphragm. The material used and the thickness of the material is based on years of research and experience. However, due to variation in the material and to manufacturing tolerances, the rupturing point of the diaphragm cannot be determined definitely prior to manufacture. It has been the practice in the art to make a number of diaphragms from one batch of material holding the tolerances, such as dimensions, etc., as nearly as possible to a desired Value and then to test a certain percentage of the diaphragms made from one batch of material to destruction, and assume or trust that the structure of the remaining diaphragms will be within certain limits of the average rupturing capacity of those tested. v

If at a later date it is desired to determine the then rupturing capacity of the diaphragm which may have changedwith the ageingfof the material, or from subjecting the diaphragms to varying pressures less than its rupturing capacity, it is again necessary to test a certain number of such diaphragms to destruction and again assume that the rupturing pressure of the remaining diaphragms is somewhere in the vicinity of the average of those tested. Usually when this is done, the diaphragms tested are not all from the same batch of material and consequently the test results are more scattered.

It is an object of my invention to provide a relief device which avoids the above-named limitations and which may be tested at any time during its operating life to determine the pressure at which it operates and which maybe adjusted at any time during its life to operate at a desired pressure.

Other objects and advantages of the inven tion will be apparent from the followin description of a preferred embodiment of the invention, reference being had to the accompanying drawings, in which:

Figure 1 is a side elevational view of an elec- I trical transformer embodying the invention; Fig. 2 is a vertical sectional view of the relief device positioned on the cover of the transformer casing;

v Fig. 3 is a horizontal sectional view taken along the line III--III of Fig. 2 and drawn at a reduced scale from Fig. 2. I Y

Referring to Figure 1 of the drawings, a transformer tank or casing l is shown containing within the casing the electrical apparatus immersed in an insulating fluid. High voltage terminal bushings 2 and 3 and low voltage termi-. nal bushings 4 and 5 are shown mounted upon the tank cover .6, together with the Pressure relief device shown generally at 1.

Referring particularly to Fig. 2 of the drawings, a pressure relief openin II is provided in the tank or casing cover 6 about the outer edge of which a cylindrical manhole ring [2 is welded as shown at H and extends'upwardly. A cover ring I5 is provided, having slots [6 at spaced intervals about its outer perimeter, as best shown in Fig. 3, and is held in position against the upper rim of the manhole ring l2 by studs ll welded to, and extending upwardly from, the tank cover 6. Washers l8 and screwthreaded nuts l9 are applied to the upper ends of the studs I! for retaining the coverv ring 15 tightly in engagement with the manhole ring 12. An annular depression 2| is provided in the upper edge of the manhole ring I2 forac commodating a gasket 22 to effect a tight joint between the members l2 and IS. The shape of the cover rin [5 is best shown in Fig. 3 and includes an inner openin outlined as shown at 23, shown as providing three lobes and having three tracks 24, two of which are shown in Fig. 2 on the underside thereof to accommodate rollers 25 attached to latch means 26, three in number, for a purpose to be presently described.

The movable portion of the release device includes a relief cover 31 for the relief device posi- 3 tioned on the outer side of the cover ring l5 in which cover ring a recess 32 is provided for containing a gasket 33 that insures a tight connection between the relief cover and the cover ring to close the discharge opening extending between the apparatus casing 6 and the outside atmosphere. A plurality of pressure bolts 34, three in number being shown, are provided and are brazed or otherwise attached to the relief cover 3|. The pressure bolts extend both above and below the relief cover 3 At the lower ends of the pressure bolts 34, a pressure ring 35 is provided which is spaced from and movable with pressure bolts 34. As shown, the lower end of the pressure bolts are threaded at 36 and provided with nuts 3'! beneath the pressure ring 35 for supporting the ring in the desired spaced relation below the level of the relief cover 3|. Projections 38 extend upwardly at spaced intervals about the pressure ring 35 which, by means of pins 39, support the several latch means 25. The latch means 26 are shown in Fig. 2 in their normal positions, corresponding to the closed position of the relief cover 3|. At the upper end of the latch means 26 a pin 4| is provided upon which is mounted the previously mentioned roller that engages the track 24. In the illustrated position of the mechanism, the relief cover 3| is held tightly against the outer surface of the cover ring l5. Any pressure within the tank on the underside of the relief cover 3| tending to raise the cover is communicated through the pressure bolts 34 to the pressure ring 35 and through the several latch means 26 and rollers 25 to the cover ring |5 to .prevent the upward movement of the relief cover. 3| so long as the latch. means 26 remain in their illustrated positions.

Each one of the latching means 25 has an inwardly extending arm carrying a pin 42 upon which a roller 43 is mounted, which roller engages the outer circumference of a latch plate 44 positioned at an elevation just above the outer projections 45 on the inwardly extending arm of the latch means 26. It will be noted that in the normal or illustrated positions of the latch means 26, the pin 4| carrying the roller 25 is slightly nearer the center or axis of the device than is the pin 39 so that as force is communicated between the pressure ring 35 and the cover ring l5 the latch means 25 will tend to rotate inwardly about the pin 39 and is prevented from doing so, so long as the latch plate 44 is in the position illustrated in Fig. 2.

Means is provided for'normally retaining the latch [plate 44 in its illustrated position when the pressure within the tank or casing l is below a predetermined value and for lifting the latch plate 44 to release the latch means 26 to cause the relief cover 3| to be raised from its seat and open communication between the interior of the casing and the outside atmosphere when the pressure within the casing exceeds a predetermined Value. The means for controlling the latch plate 44 includes a trigger 5|, a bellows 52 and a toggle mechanism shown generally at 53. The trigger 5| is shown in the form of a rod or shaft, the lower end of which extends centrally through an opening in the latch plate 44 and is provided with a nut 54 adjacent its lower end at an elevation such as torequire a limited upward movement of the trigger 5| before the nut 54 will engage the latch plate 44. A bellows plate 55 is attached to the upper end of the trigger shaft 5| and to one end of the Sylphon belthe relief cover 3| through the action of the lows 52. The lower end of the bellows 52 is attached at 56 to a plate 51 that is held by screws 58 tightly against the relief cover 3|. A gasket 59 is provided in an annular recess in the upper surface of the relief cover 3| to effect a tight seal between the plate 51 and the relief cover 3|. An opening 60 is provided centrally of the relief cover 3| so as to permit gas within the apparatus cover to flow into the chamber 6| formed by the Sylphon bellows 52 and the end plate 55 so that the pressure within the chamber 5| will correspond to the pressure within the apparatus casing I.

The toggle mechanism 53 is positioned adjacent the trigger shaft 5| at a point intermediate its ends and comprises a base portion 52 attached to the lower surface of the relief cover 3|. The toggle mechanism includes a pin 53 carried by the trigger 5| and attached to the inner ends of a pair of toggle arms 54 and 65. The outer end of the arm 54 is attached by a pin 65 to the base portion 62 of the toggle mechanism and the outer end of the arm 55 is attached by a pin 5'1 to a movable plunger 68 positioned Within a bore 69 formed in the base portion 32 of the toggle mechanism and adapted to move horizontally within said bore. The plunger 63 is provided with a central portion about which a spring H is positioned and with an end flange 12 on the inner end thereof for receiving the inner end of the spring H. The outer end of the spring 7| engages a plug 13 screw fitted into the outer end of the bore 69 in the base structure 62 of the toggle mechanism.

A shock absorber is provided including a tube of material 8| positioned about the lower'end of the pressure bolt 34 and movable therewith between two tube members 82 and 83 which are attached to and extend downwardly from the cover ring l5. When the cover 3| and the pressure ring 35 move quickly upwardly upon the tripping of the latch mechanism, the cylindrical tube 8| moves into the chamber 85 between the tubes 82 and 83 against the entrapped gas within this chamber. The upward movement of the tube 8| causes this gas to be compressed and to effect a downward force on the upper end of the tube 8| which is communicated through the washer 84 to the pressure ring 35, thus retarding the upward movement of the pressure ring 35 and relief cover 3|. One such shock absorber is associated with each of the pressure bolts 34.

A hood 9| having a generally dome-shaped top 92 and a downwardly extending flange 93 is mounted upon the upper ends of the pressure bolts 34 and held in position thereon by cap nuts 94 engaging cushioning or washer elements 95 between the cap nut and the hood.

Ihe hood moves with the relief cover 3| to which the pressure bolts 34 are attached. The lining of suitable material including a cylindrical member 96 is shown about the pressure bellows 52 surrounding the area inside of the pressure bolts 34 between the. relief cover 3| and the hood 9| and also including a top portion 97 lining the interior of the dome-shaped portion 92 of the hood.

During normal operation of the electrical transformer, the various parts of the relief device will be as shown in Fig. 2. 'As the pressure in the apparatus casing increases, the pressure in the chamber 6| of the tripping bellows 52 correspondingly increases, tending to raise the bellows end plate 55 and the trigger member 5| upwardly. So long as the pressure within the apparatus casing is below the desired value at which the relief device will trip, the trigger 5| is retained in its illustrated position by the toggle mechanism 53. The downward component of force from the arms 64 and 65 on the pin 63 caused by the pressure of the spring H is sufficient to overcome the upward pressure caused by the bellows 52 so long as the pressure within the apparatus casing is below the particular pressure at which the upward force of the bellows 52 will overcome the downward force of the spring II on the pin 63 carried by the trigger 5|. This downward force is adjusted by adjusting the plug 13 which is adapted to be moved within the bore 69 to increase or decrease the pressure on the spring 1|. If the pressure within the apparatus casing and which is applied to the bellows 52 increases sufficiently to cause the upward force on the pin 63 to increase to a value sufficient to move the pin 63 upwardly against the downward force of the toggle mechanism, the downward force on the pin 63 caused by the inherent characteristics of the toggle mechanism 53 disappears very rapidly thus permitting the bellows 52 to move the trigger 5| rapidly in an upward direction. The plunger 68, attached to the outer end of the arm 65 will be moved to the right, as viewed in Fig. 2, against the force of the spring 1| until the pin 63 is in the plane of the pivot pins 66 and 61.

During this movement, the nut 54 on the lower end of the trigger shaft 5| engages the underside of the latch plate 44, moving it upwardly from engagement with the rollers 43 thus permitting each of the latch members 26 to move inwardly and downwardly about the pin 39. This movement is caused by the component of force applied between the pressure ring 35 and the relief cover 3| which is communicated through the pivot members 39 and 4| and the roller to the track 24. As the several latch members 26 each rotate about the pin 39 in the above-described manner, the roller 25, which moves inwardly and downwardly, disengages the track 24 thus releasing the pressure normally applied from the pressure ring through the pressure bolts 34 to retain the relief cover 3| for holding it in closed position, and permitting the entire structure attached to these bolts 34 to move upwardly due to the pressure within the tank against the underside of the relief cover 3|. The gas within the apparatus cover is thus permitted to escape through the ressure opening shown at H, and between the raised relief cover 3| and the cover ring l5 into the space beneath the hood 9| and past the outer rim of the hood to the atmosphere.

After the pressure device has so operated, it is again manually returned to the position illustrated in Fig. 2, to be ready for another operation when required. This is done in the following manner. The hood 9| is removed to give access to the nuts l9 on the studs IT. The nuts I9 are then removed allowing the relief device assembly including the cover ring I5, the cover plate 3|, the pressure bolts 34 and the parts attached thereto to be raised from the apparatus cover. The assembly is then turned upside down to allow the latch means 26 to drop back by gravity to their normal positions with the rollers 25 against the tracks 24. In order to provide freedom of movement for the several latch means 26 to return to their normal positions, the nuts 31 are loosened on the bolts 34 to allow each latch means 26 to more readily position itself between 6 the pressure ring 35 and the cover ring l5. The pressure ring 35 and cover plate 3| will then be moved in a direction to close the cover plate 3| against the cover ring l5. The hood 9| may be temporarily attached in its reverse position (shown in broken lines in Fig. 2) so that the dome-shaped top 92 is forced against the bellows plate 55, forcing the trigger shaft 5| against the force of the toggle mechanism 53 in its released position, to return it to its reset or illustrated position and to return the latch plate 44 to its illustrated position between the rollers 43 carried by'the latch means 26. The nuts 31 on the ends of the pressure bolts are then tightened against the pressure ring 35 to bring the rollers25 carried by the latch means 26 tightly against the tracks 24 on the cover ring I5 and force the cover plate 3| tightly into position against the gasket 33 in the cover ring |5. The relief device assembly is then turned right side up and replaced on the cover of the apparatus casing. The nuts |9 are replaced on the studs l1 and tightened to hold the cover plate I 5 tightly against the gasket 22 in the manhole ring |2. The hood 9| is then removed from its reversed position shown in broken lines and replaced in its normal position shown in full lines in Fig. 2.

The pressure device may be tested at any time during its life by applying pressure tothe apparatus sufiicient to cause the relief device to.

operate and by measuring the pressure required to operate it. If the device operates at a pressure other than that desired, the toggle spring may be adjusted by screw threading the plug 13 further into or further out of the bore in which it is positioned to adjust the tension of the spring H to the value necessary to effect oper ation of the device at the desired pressure.

It occasionally becomes desirable to test the apparatus casing for tightness above the pressure at which the pressure relief device trips. When it is desired to do this, the cap nuts 94 at the top of the pressure bolts 34 are removed and the hood 9| is removed from its normal position and turned upside down and reattached in the position shown in the dot and dash line 99. In this position of the hood, the central dome-- shaped portion 92 thereof engages the bellows; plate 55 at the end of the tripping bellows 52, thus preventing the bellows from expanding due to the pressure within the chamber 6|, and preventing the trigger 5| from being moved above its illustrated position, making the tripping mechanism inoperative. In this position of the hood, the relief device cannot trip to relieve the pressure within the tank. The hood should, therefore, always be applied with the outer rim 93 thereof extending downwardly about the operating mechanism of the device when put into service.

Modifications in the apparatus illustrated and described will occur to those skilled in the art and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. A casing having a discharge opening there in, a pressure retainer and relief device having a relief cover normally positioned for closing said discharge opening, means for normally holding said relieve cover in closed position including latch means normally positioned for communieating pressure applied to the inner side of the relief cover to the casing to retain the relief cover in closed position and a latch plate for normally retaining the latch in latched position', and means operative-upon a predetermined pressure within the casing for operating the latch plate to release the latch and effect the operation of said relief cover to establish communication between the inside of the casing and the outside atmosphere, a plurality of pressure bolts attached to the latch plate and extending upwardly from the relief cover and a hood mounted on the upper ends thereof and extending over and downwardly about the relief cover and the operating mechanism for operating the latch plate. a

2. A casing having a discharge opening therein, a pressure retainer and relief device having a reliefcover normally positioned for closing said discharge opening, means for normally holding said relief cover in closed position including a cover ring disposed about the opening and fixedly attached to the casing cover in spaced relation thereto and against the outer side of which the relief cover is retained, a pressure ring supported from the relief cover within the casing below the cover ring, latch means normally positioned between the pressure ring and the cover ring for'holding the relief cover tightly against thev outer surface of the cover ring, a latch plate for normally holding the latch means in latching position, and means operative upon a predetermined pressure within the casing for operating the latch plate to release the latch means and effect the operation of said relief cover by the pressure within the casing to open the discharge opening of the casing.

3. A casing having a discharge opening therein, a-pressure retainer and relief device having a relief cover normally positioned for closing said discharge opening, means for normally holding said relief cover in closed position including latch means normally positioned for communicating pressure applied to the inner side of the relief iii) cover to the casing to retain the relief cover in closed position and a latch plate for normally retaining the latch in latched position, and means for operating the latch plate to re-' lease the latch means and effect the movement of the retainer cover to an open position comprising a trigger shaft having one end extending through an opening in the latch plate and the other end extending upwardly, a tripping bellows responsive to the pressure within the casing and op-eratively connected to the upper end of the trigger shaft, and means including a toggle mechanism for normally biasing said trigger shaft downwardly against the force of the tripping bellows and subject upon a predetermined pressure on the tripping bellows to be'abruptly actuated upwardly thereby for actuating the latch plate to release the latch i. A casing having a discharge opening therein, a pressure retainer and relief device having a relief cover normally positioned for closing said discharge opening, means for normally holding said relief cover in closed position including a cover ring fixedly attached to the casing exteriorly thereof and against the outer side of which the relief cover is retained, a pressure ring supported from the relief cover within the casing below the cover ring, a plurality of latch means pivotally mounted on the cover ring normally positioned between the pressure ring and the cover ring for holding the relief cover tightly against the outer surface of the cover ring, a latch plate normally positioned between the several latch means for holding them in latching position, and means for operating the latch plate to release the 8, latch means and effect the movement of the relief cover to an open position comprising a trigger shaft having one end extending through an opening in the latch plate and a toggle mechanism connected to said trigger for normally biasing the trigger to an inactive position, and a tripping 1bellows responsive to the'pressure within the casing for actuating the trigger against the bias ofthe toggle mechanism for actuating the latch plate to release the latch means.

5. A casing having a discharge opening therein, a pressure retainer and relief device having a relief cover normally positioned. for closing said discharge opening, means for normally holding said relief cover in closed position including latch means' normally positioned for communicating pressure applied to the inner side of the relief cover to the casing toiretain the relief cover in closed position and a latch plate'fornormally retaining the latch'inj latched position, and means for operating the latch plate to release the latch means and effect the 'movement of the relief cover to an open position comprising a trigger shaft having one end extending through an opening in the latch plate and the other end extending upwardly, a trippingbellows fresp'onsivei to the pressure within the. casing and operatively connected to the upper end of the trigger shaft, and means including a toggle. mechanism for normally biasing said trigger shaft downwardly against the force of the tripping bellows and subject upon a predetermined pressure on the tripping bellows to be abruptly actuated upwardly thereby for actuatingthe latch plate to release the latch, a plurality of .pressure bolts attached to the relief cover and a hood mounted on they upper ends thereof and extending over and downwardly about the relief cover'and the trigger opi crating mechanism.

6. A casing having adischarge opening therein, a pressure retainer and relief device having a relief cover normally positioned for closing said- 1 wardly, a tripping bellows responsive to the pressure Within the casing and operatively connected,

to the upper end of the trigger shaft, and means including a toggle mechanism for normally biasing said trigger shaft downwardly against the force of the tripping bellows and subject upona predetermined pressure on the tripping bellows tobe abruptly actuated upwardly thereby for actuating the latch plate to release the latch, a plurality of pressure bolts attached to the relief cover and extending downwardly therefrom, and shockabsorbing means cooperating therewith to retard the upward movement of the relief cover upon release of the latch means.

7. A casing having a discharge opening therein, a pressure retainer and relief device having a relief cover normally positioned for closing said discharge opening, means, for normally holding said relief cover in closed position including a cover ring fixedly attached to the casingexteriorly thereof and against the outer side of Whichthe relief cover is retained, a pressure ring supported from the relief cover within the casing below the cover ring, a plurality of latch means normally positioned between the pressure ring and the cover ring for holding the relief cover tightly against the outer surface of the cover ring, each of the latch means having a roller carried at its upper end for engaging a separate track provided on the relief cover, and each latch means having an inwardly extending arm having a roller mounted thereon, a horizontal latch plate normally positioned against the last-named rollers for normally holding the latch means in latching position, and means operative upon a predetermined pressure within the casing for op erating the latch plate to release the latch means and effect the operation of said relief cover.

8. A casing having a discharge opening therein, a pressure retainer and relief device having a relief cover normally positioned for closing said discharge opening, means for normally holding said relief cover in closed position including latch means normally positioned for communicating pressure applied to the inner side of the relief cover to the casing to retain the relief cover in olosecl position and a latch plate for normally retaining the latch in latched position, and means for operating the latch plate to release the latch means and effect the movement of the relief cover to an open position comprising a trigger shaft 10 having one end operatively connected for operating the latch plate and the other end operatively connected to a tripping bellows responsive to the pressure within the casing, and a spring biased toggle mechanism normally biasing said trigger REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 201,468 Tregoning et a1. Mar. 19, 1878 1,143,669 Watrous June 22, 1915 1,413,530 Burnham June 6, 1922 1,526,512 Teten Feb. 17, 1925 1,792,302 Hilliard Feb. 10, 1931 1,840,060 Show Jan. 5, 1932' 1,897,076 Shand Feb. 14, 1933 1,963,518 Bradley a June 19, 1934 2,070,661 Hughes Feb. 16, 1937 2,297,003 Larson Sept. 29, 1942 2,367,989 Alders Jan. 23, 1945 

